Rotary seal with relief angle for controlled tipping

ABSTRACT

A sealing device for sealing the gap between two relatively moving members is provided with a pivot point on its cross-sectional perimeter. As pressure against the seal increases, the seal rotates about the pivot point, resulting in an increased sealing surface area on the seal. Additionally, a recess is provided on the cross sectional perimeter, advantageously offering a more frictionless sealing relationship between the seal and the moving member. Further, a recess is provided on outer portion of the cross sectional perimeter on a surface of the seal that would contact an energizer ring, the recess eliminating a dynamic interface between the energizer ring and the seal.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the invention.

[0002] The present invention relates to an improved rotary seal andenergizer with pressure balancing and improved lubrication properties.

[0003] 2. Description of the related art.

[0004] Prior seals have limitations when given an applied pressure andrelative velocity, i.e., when a sealed rod is rotated. In operation,typical pressure applications occur at 3000 PSI and above, and fairlylow surface velocity movement of 10 to 50 feet per minute.

[0005] Due to the rotary motion and poor lubrication, the constantfriction can lead to heat generation increases, thereby acceleratingwear and causing seal extrusion and loss of material. During sealpressurization, the seal slides over in the groove and the energizerforms up in a corner creating a heavy load, resulting in high friction.This high friction accelerates heat generation, compression set, andpossible loss of seal ring energization, which may also result in thecreation of an undesirable dynamic interface created between theenergizer and seal ring, thus producing undesirable abrasion and wear tothe energizer.

SUMMARY OF THE INVENTION

[0006] To improve those situations, the present invention includes apressure balance design which reduces overall friction during operationand improves the lubrication underneath the seal ring. Preliminaryresults indicate a reduction of torque of over fifty percent. Heatgeneration is also reduced by nearly fifty percent and an improvedleakage control is also evident.

[0007] The seal ring of the present invention includes a lower centergroove. The center groove is in the contact space between the seal ringand rod. The groove minimizes the bottom contact area, thus increasingthe contact stresses and improving leakage control. When the system ispressurized, the seal ring pivots about a point on the bottom surfacecontact area, thereby providing a pressurized seal contact along alarger bottom contact area, while maintaining an extrusion resistantchamfer.

[0008] In the invention, a seal for sealing a gap between a first memberand a second member moving relative to the first member comprises a ringwith a cross section, the cross section having a pivot point and aperimeter. When external pressure is applied to the ring, for instancewith the addition of fluid pressure, the ring responds by rotating aboutthe pivot point.

[0009] In another embodiment of the invention, a seal arrangement isprovided for sealing a gap between a first member and a second member,the second member moving relative to the first member, the sealarrangement comprising a first ring and a second ring. In thisembodiment, the first ring has a cross section with a perimeter and apivot point, the first ring pivoting about the pivot point when externalpressure is applied. Additionally, a second ring is provided with across section and a perimeter.

[0010] In yet another embodiment of the invention, a seal for sealing agap between a first member and a second member moving relative to thefirst member includes a ring having first surface and a second surface,the second surface sealingly engaging with the second member when theseal is subjected to external forces, and the second surface disengagingwith the second member when the external forces are absent.

[0011] In a further embodiment of the invention, the seal arrangementcomprises a first ring having a cross section with a perimeter, a firstlip, a second lip, and a recess defined between the first lip and thesecond lip. Additionally, a second ring is provided and disposed betweenthe first member and the first ring, the second ring having a perimeterthat protrudes into the recess of the first ring during a pressurizedstate, and spans the recess during a non-pressurized state.

[0012] In an alternative embodiment of the invention, a sealingstructure for sealing a gap between two machine parts arranged formotion relative to each other comprises a sealing ring having an innersurface facing the second machine part, the inner surface having a pivotpoint, a first lip, a second lip, a recess defined between the first andsecond lip, and an outer surface facing toward the first machine part,the sealing ring pivoting about the pivot point when exposed to externalpressure. Additionally, an energizer ring is provided having a crosssection with a perimeter, the energizer ring being disposed between theouter surface and the first machine part.

[0013] Yet another embodiment of the invention can be described as amethod of sealing a gap between a first member and a second member, thesecond member moving relative to the first member, the method comprisingthe step of providing a ring capable of pivoting about a cross sectionalpoint when subjected to external pressure.

[0014] The present invention is advantageous over the prior art seals inthat it provides a sealing surface that increases in surface area aspressure against the seal escalates, while providing a high contactpressure profile at the sealing apex to improve leakage control. Theincreased sealing surface is accomplished by the rotation of the sealmember during pressurized states, thereby placing a larger part of theseal in contact with a machine part when most needed.

[0015] It is a further advantage of the present invention that a reducedsealing surface is provided during low pressure operation. When the sealis in a low pressure state, and rotation about a pivot point has not yetoccurred, the present invention advantageously provides a recess alongits sealing surface, thereby reducing the amount of friction between themachine part and the seal.

[0016] It is yet another advantage of the present invention that atapered wall is provided on a side of the seal, the tapered wall servingto firmly hold the seal in an ideal location against a surface of theseal housing once the seal has rotated about the pivot point.

[0017] It is a further advantage of the present invention that a recessis provided on the top surface of the seal, for interaction with anenergizer ring. By providing a recess, ridge, bump, or other means ofincreasing surface area and simultaneously introducing localized highstresses, facing the energizer ring, the edges of the seal's recesstransmit deforming pressure to the surface of the energizer ring duringa pressurized state, thereby greatly increasing the coefficient offriction and/or the contact surface area, and consequently substantiallyeliminating a dynamic interface between the energizer ring and the seal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention will be better understood by reference to thefollowing description of an embodiment of the invention taken inconjunction with the accompanying drawings, wherein:

[0019]FIG. 1 is a fragmentary, sectional view on an axial plane andillustrating one form of seal construction of this invention;

[0020]FIG. 2 is a fragmentary, sectional view of a prior art sealconfiguration;

[0021]FIG. 3 is a fragmentary, sectional view of the seal element of thepresent invention;

[0022]FIG. 4A shows an FEA graph of a Prior Art seal system, installedin an unpressurized state;

[0023]FIGS. 4B through 4D show FEA graphs of different embodiments ofthe present invention, installed in an unpressurized state, showingalternate energizers;

[0024]FIG. 5A shows an FEA graph of the embodiment shown in FIG. 4Aunder a high pressurization;

[0025]FIGS. 5B through 5D show FEA graphs of the embodiments shown inFIGS. 4B through 4D under a high pressurization;

[0026]FIG. 6 is a graph showing the results of a breakout torque testcomparing the prior art design to the design shown in FIG. 1;

[0027]FIG. 7 is a graph showing the results of a dynamic torque test atlow velocity comparing the prior art design to the design shown in FIG.1;

[0028]FIG. 8 is a fragmentary, sectional view on an axial plane andillustrating one form of seal construction of this invention;

[0029]FIGS. 9A through 9C are graphs showing the results of anaccumulated leakage test at high pressure comparing the prior art designto the design shown in FIG. 1;

[0030]FIGS. 10A and 10B are graphs showing the results of an accumulatedleakage test at medium pressure comparing the prior art design to thedesign shown in FIG. 1;

[0031]FIGS. 11A and 11B are graphs showing the results of a wear test atmedium comparing the prior art design to the design shown in FIG. 1; and

[0032]FIGS. 12A through 12C are graphs showing the results of a weartest at high pressure comparing the prior art design to the design shownin FIG. 1.

[0033] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplification set out hereinillustrates one preferred embodiment of the invention, in one form, andsuch exemplification is not to be construed as limiting the scope of theinvention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Referring now to the drawings and particularly to FIG. 1, thereis shown a construction which includes an annular seal assembly 13, anouter member 15 having an annular seal groove or gland 17 in which theseal assembly is mounted, 19. Fluid under pressure is applied to theseal assembly 13 in the direction of arrow P. The fluid passes throughan annular clearance space 20 and acts directly on the seal assembly 13.It should be understood that members 15 and 19 are merely illustrativeof one environment in which the seal assembly 13 can be advantageouslyutilized. In the embodiment illustrated, the members 15 and 19 aremounted for relative rotational movement.

[0035] Although the outer member 15 could be of various differentconfigurations, in the embodiment illustrated, it includes axiallyspaced, radially extending walls 21 and 23 interconnected by an axialwall 25 to define the seal gland 17. The seal gland 17 completelycircumscribes the inner member 19. In the embodiment illustrated, sealgland 17 is generally rectangular in an axial cross-section. The outermember 15 has a passage 27, extending there through, in which the innermember 19 is positioned.

[0036] The inner member 19 can be of various different configurations;however, in the embodiment illustrated, it is in the form of cylindricalshaft. The inner member 19 has the cylindrical outer surface 29, whichdefines one of the surfaces to be sealed.

[0037] The seal assembly 13 includes a seal element 30 and an annularresilient elastomeric member which, in the embodiment illustrated, is inthe form of an o-ring elastomer 33. The elastomer energizer can beutilized in nearly any common form, as shown in FIG. 8. The seal element30 can be constructed of any of the materials commonly used for thispurpose, for example, a suitable plastic material such as thermoplasticmay be used. Polytetrafluoroethylene (PTFE), thermoplastic elastomer(TPE), polyurethane (PU), and ultra high molecular weight polyethylene(UHMWPE) are examples of thermoplastics that can be utilized. Analternate embodiment of the system is shown in FIG. 8, having an element30 with a different top surface.

[0038] The construction of the seal element 30 can best be understoodwith reference to FIG. 3, which shows the element isolated by itself.Generally, the seal 30 is of an annular configuration having a bottomsurface A including a groove 34 for low pressure sealing.

[0039] For ease of description, the outer peripheral surface of sealelement 30 will be described in relation to FIG. 3 in a counterclockwise fashion describing the different angles, edges, and surfaces.Starting from the lower left hand side, edge points 1, 2, 3, 4, 4′, 5,6, and 7 generally outline the lower bottom surface of surface element30 while points 8, 9, 10, 11, 12, 13, 14, and 15 depict the changingcontour on the top surface T of seal element 30. Generally bottomsurface A is located between points 3 and 4, 4′ and 5. This surface A isin contact with inner member 19 during a non-pressurized state of theseal assembly 13. Located between points 5 and 6 is a surface B, whichcreates an increased pressurized contact area during sealpressurization. Between points 6 and 7 is an extrusion resistantchamfer. During pressurization, seal element 30 tilts or rotates onpoint 5, bringing surface B into contact with member 19.

[0040] Between points 7 and 8 is a surface C, which is a relief angle toallow seal element 30 to tip upon edge 5 during edge sealpressurization. In the present invention, surface B and surface C aremost preferably perpendicular to one another. In other preferredembodiments, an angle between surface B and surface C may range from 85°to 95°, but more preferably from 89 to 91°. Between edges 8 and 9 andedges 14 and 15 are disposed top chamfers that are provided to eliminateelastomer nibble.

[0041] One aspect of the invention, which is different from the priorart, is the ability to balance pressure and frictional aspects. Duringpressurization, the fluid pressure acts on the area from point 1 through5 of the seal element 30 balancing against the pressure that is beinggenerated through the elastomer, so seal element 30 seals along thewidth from point 5 to point 6. At pressurization, all of the force thatis generating the torque is being driven only through point 5 to 6. Thistipping about point 5 is where torque reduction occurs. This pressurebalancing reduces the amount of load between the seal and the rod. Theradial loading is reduced by a proportion of 1:7 to 5:7. To preventextrusion, a chamfer is created between points 6 and 7.

[0042] To help facilitate the tipping or the rolling action, sealelement 30 includes a back angle. This angle, or edge C is perpendicularto edge B allowing the seal to roll in the groove. Edge C will rollperpendicular to the rod and then also be parallel with the gland wall23 during pressurization. As the elastomer 33 energizes across the topof seal element 30 it attempts to increase the friction between theelastomer 33 and the seal element 30, trying to keep the seal ring fromnot spinning with member 19, but rather to keep it within the gland 17.

[0043] To eliminate a dynamic interface, a groove, ridge, bump, or othermechanical interlock 40 is provided on the top surface, as shown inFIGS. 4B through 4D. The elastomer 33 deflects down into groove 40 andpoints 11 and 12 experience high loads. There is a high strain on theelastomer 33 in that area. There is strain reduction between points 11and 12. There is no seal element to support the elastomer 33 in groove40, so the elastomer 30 deforms down in the groove creating a highstress concentration at 11 and 12. This increases the frictionalproperties and/or torque between the elastomer component 33 and the sealring component 30, thereby providing a non-slipping and interlockingrelationship between elastomer component 33 and seal ring component 30.Other modes of generating the increased friction are to increase thecontact surface area between elements 30 through 33. Such increase isaccomplished by changing the shape.

[0044] Elastomer 33 deflects as the seal element 30 is rolled over, anda stress concentration is also created therein. From point 10 down topoint 9 there is an angle or surface which operates as a strain relieffor the energizer. There is another such surface from the front sidepoints 13 to 14. These angles relieve the elastomer as it is beingenergized. Any relief of the elastomer there allows the elastomer 33 toabsorb some of the energy from the applied pressure. Energy from theapplied pressure is also absorbed with the deformation of elastomercomponent 33 into groove 40 on the top surface and the chamber formed bythe chamfered edge disposed between points 8 and 9.

[0045]FIGS. 4A through 5D show a finite element analysis of the normalcontact stresses on the present invention in contrast to a prior artseal. FIGS. 5B through 5D shows the advantageous reduction of thecontact area when the seal arrangement is pressurized. Thegreater-than-50% reduction in the contact area provides torque, heatgeneration, and frictional improvements compared to the prior art sealproducts.

[0046]FIGS. 6 through 12 show the advantages of the present inventionwith results of finite element analysis comparing the prior art seal tothe present invention. The analysis was conducted using a test glandwith tested surface velocities over the seal including low, medium, andhigh surface velocity, having constant rotation, and being subjected tolow, medium, or high pressure for a duration of 200,000 cycles. Thesurface finish was in the range of 0.1 to 0.2 μm.

[0047]FIG. 6 displays the improved break-out torque results of thepresent invention over the prior art. FIG. 7 shows the dynamic torqueimprovements of the present invention over the prior art at lowvelocity. FIGS. 9A through 9C show accumulated leakage comparisonsbetween the present invention and the prior art at high pressure. FIGS.10A and 10B shows accumulated leakage comparisons between the presentinvention and the prior art at medium pressure. FIGS. 11A and 11B showwear result comparisons between the present invention and the prior artat medium pressure. FIGS. 12A through 12C show wear result comparisonsbetween the present invention and the prior art at high pressure. Whilethis invention has been described as having a preferred design, thepresent invention can be further modified within the spirit and scope ofthis disclosure. This application is therefore intended to cover anyvariations, uses, or adaptations of the invention using its generalprinciples. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A seal for sealing a gap between a first memberand a second member moving relative to the first member, said sealcomprising: a ring having a cross section with a pivot point in responseto external pressure.
 2. The seal of claim 1, wherein said crosssectional perimeter includes a secondary sealing portion adjacent saidpivot point, said secondary sealing portion engaging with the secondmember during a pressurized state, and disengaging with the secondmember during a non-pressurized state.
 3. The seal of claim 1, whereinsaid cross sectional perimeter includes a first rim adjacent said pivotpoint, a second rim, and a recess defined there between.
 4. The seal ofclaim 3, wherein said recess faces the second member during anon-pressurized state.
 5. The seal of claim 3, wherein said first rimand said second rim engage the second member during a non-pressurizedstate.
 6. The seal of claim 3, wherein said second rim disengages fromsaid second member during a pressurized state.
 7. The seal of claim 3,wherein said recess faces the first member.
 8. The seal of claim 3,wherein said recess faces an energizer ring.
 9. The seal of claim 1,wherein said ring is disposed within a gland defined by the firstmember, said gland facing the second member.
 10. A seal arrangement forsealing a gap between a first member and a second member, said secondmember moving relative to said first member, said seal arrangementcomprising: a first ring having a cross section with a perimeter and apivot point, said first ring pivoting about said pivot point whenexternal pressure is applied to said seal arrangement; and a second ringhaving a cross section with a perimeter.
 11. The seal arrangement ofclaim 10, wherein said first ring and said second ring areconcentrically disposed.
 12. The seal arrangement of claim 10,-whereinthe first member defines a cavity for housing said first ring and saidsecond ring.
 13. The seal arrangement of claim 10, wherein said firstring perimeter further includes a pressurized seal portion, saidpressurized seal portion engaging the second member during a pressurizedstate and disengaging from the second member during a non-pressurizedstate.
 14. The seal of claim 10, wherein said first ring perimeterincludes a first rim adjacent said pivot point and a second rim with arecess defined there between.
 15. The seal of claim 14, wherein saidrecess faces the second member during a non-pressurized state.
 16. Theseal of claim 14, wherein said first rim and said second rim engage thesecond member during a non-pressurized state.
 17. The seal of claim 14,wherein said second rim disengages from the second member during apressurized state.
 18. The seal of claim 14, wherein said recess facessaid second ring.
 19. The seal of claim 28, wherein said second ringperimeter protrudes into said recess during a pressurized state.
 20. Aseal for sealing a gap between a first member and a second member movingrelative to each other, said seal comprising: a ring having a firstsurface and a second surface, said second surface enqaging with thesecond member when said seal is subjected to external forces, and saidsecond surface disengaging from the second member when said seal is notsubjected to external forces.
 21. The seal of claim 20, wherein saidfirst surface comprises a first portion and a second portion.
 22. Theseal of claim 21, wherein said first portion and said second portiondefine a recess there between.
 23. The seal of claim 22, wherein saidrecess faces the second member.
 24. The seal in claim 22, wherein saidrecess faces toward the first member.
 25. The seal of claim 21, whereinsaid second portion is adjacent said second surface.
 26. The seal ofclaim 21, wherein said first portion engages with the second memberduring a non-pressurized state, and disengages with the second memberduring a pressurized state.
 27. The seal of claim 20, wherein said ringis disposed within a chamber defined in the first member.
 28. The sealof claim 20, further comprising a second ring disposed between said ringand the first member.
 29. A seal arrangement for sealing a gap between afirst member and a second member moving relative to said first member,said seal arrangement comprising: A first ring having a cross sectionwith a perimeter, a first lip, a second lip, and a recess definedbetween said first lip and said second lip, said recess facing the firstmember; and a second ring having a cross sectional perimeter, saidsecond ring disposed between said first ring and the first member, saidsecond ring perimeter protruding into said recess during pressurizedstate, and said second ring perimeter spanning said recess during anon-pressurized state.
 30. The seal arrangement of claim 29, whereinsaid second ring is an energizer.
 31. The seal arrangement of claim 29,wherein said first ring is a seal element.
 32. The seal arrangement ofclaim 29, wherein said first ring and said second ring areconcentrically aligned.
 33. The seal arrangement of claim 29, whereinsaid first rim and said second rim exert deforming stresses on saidsecond ring perimeter during a pressurized state.
 34. The sealarrangement of claim 33, wherein the deforming stresses provide anincreased coefficient of friction between said first ring and saidsecond ring.
 35. A sealing structure for sealing the gap between twomachine parts arranged for motion relative to each other, said sealingstructure comprising: a sealing ring having an inner surface facing thesecond machine part, said inner surface having a pivot point, a firstlip, a second lip, and a recess defined said first lip and said secondlip, and an outer surface facing toward the first machine part, saidsealing ring pivoting about said pivot point when exposed to externalpressure; and an energizer ring having a cross section with a perimeter,said energizer ring being disposed between said outer surface and thefirst machine part.
 36. The sealing structure of claim 35, wherein saidpivot point is in contact with the second machine part.
 37. The sealingstructure of claim 35, wherein said first rim and said second rim areengaged with the second machine part when said sealing structure is in anon-pressurized state.
 38. The sealing structure of claim 35, whereinsaid second rim is disengaged from the second machine part when saidsealing structure is in a pressurized state.
 39. The sealing structureof claim 35, wherein said inner surface further includes an inclinedsurface.
 40. The sealing structure of claim 39, wherein said inclinedsurface defines a plane that is at an acute angle from the surface ofthe second machine part.
 41. The sealing structure of claim 39, whereinsaid inclined surface and said first rim engage the second machine partwhen said sealing structure is in a pressurized state.
 42. The sealingstructure of claim 35, wherein a seal gland is disposed within the firstmachine part and facing the second machine part, said seal gland housingsaid seal ring and said energizer ring.
 43. The sealing structure ofclaim 42, wherein said sealing ring further includes a wall, said wallbeing substantially radially disposed between the second machine partand said energizer ring.
 44. The sealing structure of claim 43, whereinsaid wall defines a plane that is at an acute angle from a plane definedby a surface of said seal gland when said sealing structure is in anon-pressurized state.
 45. The sealing structure of claim 43, whereinsaid wall engages a surface of said seal gland when said sealingstructure is in a pressurized stat.
 46. The sealing structure of claim35, wherein said energizer ring is an annular resilient elastomericmember.
 47. The sealing structure of claim 35, wherein said sealing ringis composed of a thermoplastic material selected form the groupconsisting of polytetrafluoroethylene, thermoplastic elastomer,polyurethane, and ultra high molecular weight polyethylene.
 48. Thesealing structure of claim 35, wherein said sealing ring furtherincludes a chamfered edge on said inner surface.
 49. A method of sealinga gap between a first member and a second member, said second membermoving relative to said first member, comprising the step of providing aring capable of pivoting about a cross sectional point when subjected toexternal pressure.
 50. The method of claim 49, further comprising thestep of defining a recess on a surface of said ring.
 51. The method ofclaim 50, wherein said recess faces the second member.
 52. The method ofclaim 50, further comprising the step of providing a second ring, saidsecond rind being disposed between said ring and said first member. 53.The method of claim 52, wherein said second ring protrudes into saidrecess during a pressurized state.
 54. The method of claim 52, whereinsaid second ring protrudes into said recess during a pressurized state.55. The method of claim 49, further comprising the step of providing anangled surface on said ring surface, said angled surface defining aplane at an acute angle from the second member during a non-pressurizedstate, and said angled surface engaging the second member during apressurized state.
 56. The method of claim 49, further comprising thestep of providing a chamfered edge on a surface of said ring, saidchamfered edge substantially preventing the extrusion of said ring froma ring housing.